Social media optimization (SMO) is a set of methods for generating publicity through social media, online communities and community websites. Methods of SMO include adding RSS feeds, social news buttons, blogging, and incorporating third-party community functionalities like images and videos.
http://www.linkedin.com/
http://www.facebook.com/
http://twitter.com/
Social bookmarking is a method for Internet users to share, organize, search, and manage bookmarks of web resources. Unlike file sharing, the resources themselves aren't shared, merely bookmarks that reference them.
Digg.com
StumbleUpon
Reddit.com
Blue Dot
Diigo
LookSmart’s Furl
GiveALink
My Web
Netvouz
Ma.gnolia.com
Simpy
Thoof
SiteBar
SWiK
